Aircraft icing has been a concern almost since powered flight began. There have been hundreds of fatal accidents where aircraft icing was the primary cause or a contributing factor. A few of the more notable icing induced accidents within the last twenty years include American Eagle Flight 4184 near Chicago, Ill., Colgan Air Flight 3407 near Buffalo, N.Y., and Air France Flight 447 over the South Atlantic. Each one of these incidents resulted in the loss of all passengers and crew on board.
There are a variety of known icing condition detectors for aircraft. These include sensors with vibrating elements (frequency changes with ice accretion) and rotating elements (electrical load increases in icing conditions). Other sensors detect icing conditions by sensing moisture along with temperatures below freezing.
However, conventional electro-mechanical aircraft icing condition detectors require a probe or optical element to protrude from the outside of the aircraft. Undesirably, these probes or optical elements typically require adding a hole to the aircraft's fuselage to receive the probe or optical element, thereby compromising the structural integrity of the aircraft.